1/64. Use of atrial and bifocal cardiac pacemakers for treating resistant dysrhythmias.Several permanent cardiac pacing techniques have been utilized to control resistant cardiac arrhythmias. SA block, sinus arrest and intermittent ventricular tachycardia was controlled by the use of an atrial 'J' catheter and a rate programmable demand pacemaker. When these arrhythmias were associated with AV conduction delay they were managed with an AV sequential pacemaker with the additional insertion of a ventricular pacing lead. Appropriate adjustment of the AV sequential interval inhibited reciprocal AV or VA reentry thus controlling reciprocal tachycardia. Frequent ventricular premature systoles or intermittent ventricular tachycardia with in appropriately delayed sinus or subsidiary escape cycle lengths appear best managed by an AV sequential pacemaker by adjusting the atrial return cycle. Intractable atrial reentry tachycardias appear best managed by paired or rapid atrial stimulating pacemakers. Development of variable atrial rate, AV sequential and atrial return cycle activating pacemakers offer an effective control of resistant cardiac arrhythmias.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
2/64. tachycardia during resistance exercise: a case study.A male weight-trained (WT) subject (A; age = 21 years, height = 193.6 cm, body weight = 113.4 kg, parallel barbell squat 10 repetition maximum [RM] = 183.7 kg) and a group of 18 similarly trained men (WT; X /- SD; age = 24.7 /- 3.0 years, height = 180.2 /- 4.3 cm, body weight = 86.9 /- 10.7 kg, 10 RM = 127.9 /- 28.6 kg) were monitored during a barbell squat resistance exercise session (50% - 100% 10 RM) and a graded exercise test on a cycle ergometer. Compared with the WT group, heart rate (HR) for subject A was consistently > or =2 SD greater during resistance exercise (peak HR for 100% 10 RM = 212 b.min(-1) and 165.3 /- 16.2 b.min(-1)). The graded exercise test resulted in similar HR responses for both A and controls. Subject A's augmented HR was present only during the pressure load of heavy resistance exercise, and not during the volume load of endurance exercise. The data suggest that subject A may be utilizing a different mechanism for heart rate regulation during resistance exercise.- - - - - - - - - - ranking = 0.33333333333333keywords = cycle (Clic here for more details about this article) |
3/64. Bigeminal ventricular tachycardia with Wenckebach exit block.A patient is presented in whom repeated attacks of ventricular tachycardia occurred. His last and fatal attack revealed an alternation or coupling of the cycle lengths of the ventricular beats. A large left ventricular wall aneurysm was found, which probably accounted for the unusual arrhythmias.- - - - - - - - - - ranking = 0.33333333333333keywords = cycle (Clic here for more details about this article) |
4/64. Effects of the pacing site on A-H conduction and refractoriness in patients with short P-R intervals.His bundle recordings were studied in four patients with short P-R and A-H intervals, and narrow QRS complexes, who had experienced several episodes of supraventricular tachyarrhythmias. The heart was paced from the high right atrium (HRA) and the coronary sinus (CS). In three patients the A-H Wenckebach phenomenon occurred at higher rates (greater than 200 pacing beats/min) when the CS was paced than when pacing was performed from the HRA. Moreover, CS stimulation produced smaller increments in the A-H interval than did pacing from HRA. The extrastimulus method of testing was done. In cases 1 and 2 the functional refractory period of the A-H tissues was 15 to 25 msec shorter during CS pacing than when pacing from the HRA. In case 3, the low right atrium (LRA) as well as the other two sites were paced. A type 1 gap was seen from HRA, a type 2 gap from CS, and both types appeared when the LRA was paced. Case 4, in which the mid-right atrium (MRA) was also stimulated, had a double pathway from HRA and CS with conduction through the accessory pathway late in the cycle and through the A-V node earlier in the cycle. However, the A-V node could not be penetrated during MRA stimulation. It appeared that the pacing site influenced the A-H conduction pattern and refractoriness, possibly by changing the site and/or mode of entry of the stimulus into the pathways that are responsible for this syndrome.- - - - - - - - - - ranking = 0.66666666666667keywords = cycle (Clic here for more details about this article) |
5/64. Frequency and output-dependent change in conduction over slow pathways in a patient with sustained ventricular tachycardia unrelated to coronary artery disease.In a patient with sustained ventricular tachycardia, we obtained two different paced QRS morphologies from a single pacing site. In one QRS morphology the stimulus to the QRS complex was long, 150 msec, and in the other it was 100 msec. At the paced cycle length of 600 msec and the stimulus output of 4 V, one QRS morphology with the stimulus to the onset of QRS activation (St-QRS) interval of 150 msec was observed. At the paced cycle length of 400 msec, the other QRS morphology with a St-QRS interval of 100 msec was observed alternatively with the former. At the paced cycle length of 353 msec or 316 msec, the latter with a shorter St-QRS interval was exclusively observed. When the stimulus output was increased from 4 to 10 V, keeping with the paced cycle length at 400 msec, the St-QRS interval was shortened from 100 to 80 msec. For the two QRS morphologies with two St-QRS intervals, two slowly conducting pathways would be responsible. The site of the block in the faster pathway must be located at the proximity of the pacing site and the conduction at a shorter paced cycle length would be explained by "supernormal conduction."- - - - - - - - - - ranking = 1.6666666666667keywords = cycle (Clic here for more details about this article) |
6/64. Persistent tachycardia with a 2:1 exit block within an isolated pulmonary vein.We describe a patient with drug-resistant, paroxysmal atrial fibrillation who underwent segmental pulmonary vein (PV) isolation. After complete isolation of the right superior PV, a persistent regular tachycardia was recorded within the vein. A tachycardia focus with a cycle length of 114 ms was found 2.5 cm away from the ostium of the PV. The cycle lengths of the PV tachycardia near the ostium and near the focus were 400 ms and 200 ms, respectively, which indicates the presence of a 2:1 exit block within the vein. This PV tachycardia was completely eliminated with the application of radiofrequency energy at the focus.- - - - - - - - - - ranking = 0.66666666666667keywords = cycle (Clic here for more details about this article) |
7/64. Two levels of block within a pulmonary vein.We present a 37-year-old woman with drug refractory atrial fibrillation referred for a pulmonary vein (PV) isolation procedure who manifested a tachycardia with 2:1 intra-PV block within a dissociated PV. During ablation in the right superior PV, the surface rhythm became normal sinus, with persistent atrial fibrillation within the PV. Shortly thereafter, an atrial tachycardia with a cycle length of 190 ms and 2:1 distal to proximal exit block was observed within the isolated PV. Conduction block within a PV electrically isolated from the left atrium is a newly observed phenomenon that may have implications to the electrophysiologic properties of the PV muscular sleeves.- - - - - - - - - - ranking = 0.33333333333333keywords = cycle (Clic here for more details about this article) |
8/64. Intraventricular concealed double tachycardia: a case report.An electrophysiologic study was performed on a patient with ischemic sustained ventricular tachycardia (VT). During pacing at the right ventricular apex, ventricular double potential was recorded at the left ventricular apex. Sustained VT was induced by double extra stimuli from the right ventricular apex. Three types of VTs with different QRS morphologies were observed, and each VT was changeable to other types. The interval between one of the two potentials and the surface QRS was constant during all VTs, but the other potential showed dissociation from the surface QRS. During this dissociation, an intrinsic rhythm of the potential was sometimes shorter than the cycle length of the VT. The mechanism of a block between the VT and a bystander could hardly explain these electrophysiologic findings. Concealed double ventricular tachycardia was considered to be the likely mechanism.- - - - - - - - - - ranking = 0.33333333333333keywords = cycle (Clic here for more details about this article) |
9/64. Narrow QRS tachycardia with ventriculoatrial dissociation mediated by a left fasciculoventricular fiber.A 30-year-old man presented with narrow QRS tachycardia. The intracardiac electrocardiogram showed an atrial-HIS (AH) interval of 75 msec and a HIS-ventricular (HV) interval of 44 msec during baseline. Atrial incremental pacing revealed HV shortening, with apparent incomplete right bundle branch block (RBBB) morphology without QRS complex axis deviation. The induced tachycardia exhibited several QRS morphologies: a narrow QRS, complete RBBB and complete left bundle branch block (LBBB) morphology. Spontaneous conversion of the QRS pattern from wide to narrow was observed. The cycle length of the tachycardia was significantly shortened (from 316 to 272 ms) from LBBB morphology to narrow QRS complex. The atrial activation was dissociated from the ventricular activation during all tachycardias. Each QRS complex during tachycardia was preceded by a HIS deflection and HV interval was 35 ms, which was shorter than that of sinus rhythm. HIS deflection was earlier than right bundle potential during all kinds of tachycardia. This tachycardia is most likely mediated by a left fasciculoventricular fiber which connects the HIS bundle below the atrioventricular node to the myocardial tissue of the left ventricle. The HIS-Purkinje system is used as an antegrade conduction limb and the fasciculoventricular fiber as a retrograde limb in the tachycardia circuit.- - - - - - - - - - ranking = 0.33333333333333keywords = cycle (Clic here for more details about this article) |
10/64. ventricular fibrillation following elective cardioversion in a patient with permanent pacemaker.Elective cardioversion was undertaken in a patient with a VVI pacemaker and atrial tachyarrhythmia after converting the pacemaker to a VOO mode of function. The cardioverter output energy was unwittingly synchronized to the pacemaker output pulses that were falling randomly in various portions of the cardiac cycle. This resulted in the cardioverter DC shock being discharged in the ST segment of the native QRS with consequent ventricular fibrillation.- - - - - - - - - - ranking = 0.33333333333333keywords = cycle (Clic here for more details about this article) |
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